Surface modifications of an aluminum-magnesium alloy through reactive stir friction processing with titanium oxide nanoparticles for enhanced sliding wear resistance

Reactive friction stir processing (RFSP) has been employed to modify the surface properties of AA5052 Al-Mg alloy through grain refinement and the distribution of ultrafine hard nanoparticles (2 to 6% volume fractions of 50 nm titanium dioxide). The heat generated induced solid state reactions between the metal matrix and the reinforcement to form Al3Ti/MgO inclusions. The role of grain refinement and distributed hard nanoparticles on the tribological behavior of the alloy under dry sliding wear condition was evaluated. The wear rates and friction coefficient as well as macro- and micro-features of the worn surfaces indicate that the wear mechanism (at 3-7 kgf and 0.5 m/s) is abrasive. The wear rate decreased with increasing volume fraction of the hard inclusions with a significant reduction in the friction coefficient. The wear resistance could be improved > 125% (compared with the annealed alloy) at 6 vol% TiO2. The relations between the enhanced wear resistances, the microstructural changes and mechanical properties have been characterized.